Live roller conveyors, having a frame and a plurality of transverse, belt-driven rollers, are well known in the art. It often is desirable to provide one or more sections of such a conveyor that are capable of accumulating articles being conveyed when a stoppage of article movement occurs downstream on the line. Such a stoppage might occur, for example, when the flow of articles is irregular, and a downstream portion of the handling process is unable to keep up with an increased flow. Irregular flow may occur when conveyor lines crisscross, or a conveyor system may include a sorting area. It may be desirable to stop or slow down a conveyor for hand loading or packaging, or for checking labels, which sometimes is called "singulating out".
While articles can be stopped by simply blocking them on a conventional live-roller conveyor, as more and more articles build up, increased pressure is produced on the downstream articles. Such pressure can produce crushing of the articles, can throw articles off the conveyor, and a large buildup produces extremely high horsepower demands. Damage to articles by pressure buildup is a considerable and sometimes expensive problem. For instance, a very delicate article may be moving along the conveyor between a pair of very heavy articles. Unless the articles are stopped or "accumulated" on the conveyor, the delicate and sometimes expensive articles are damaged by crushing between the larger and heavier articles. Such a problem is not solved by many accumulating conveyors presently available.
For instance, an accumulating conveyor system might include a plurality of load-carrying rollers rotatably mounted between generally parallel frame sides. A plurality of lifting rollers are rotatably mounted between the frame sides beneath the load-carrying rollers. A drive belt extends between the load-carrying rollers and the lifting rollers for rotating the load-carrying rollers in response to the lifting rollers lifting the belt into engagement with the load-carrying rollers. A plurality of sensing rollers are disposed between selected pairs of load-carrying rollers, the sensing rollers being mounted for vertically reciprocating motion to actuate an actuator means which is effective to lift upstream lifting rollers. However, heretofore, the sensing rollers simply were, in one form or another, load-carrying rollers mounted for vertically reciprocating motion. The load-carrying rollers are rather heavy in order to support an appropriate load. When a delicate, lightweight article moves along the conveyor, the article often-times is too light to depress the load-carrying sensing roller. Consequently, the lightweight article becomes crushed between heavier articles notwithstanding the fact that the conveyor was designed for accumulating purposes.
This invention is directed to solving these problems by providing an improved accumulating conveyor which is sensitive to all articles, including very lightweight articles.